Monitoring: alerts over metrics, by event and by email (MON-25 to MON-30)

Every minute the node that calculates metrics evaluates each enabled
x:Alert, read from the registry, with metric('name') or the underscore
name. An alert fires when its condition turns true: it emits
telemetry.alert-event with the rendered message, and queues one email per
recipient through the outbound queue, placeholders filled and
Auto-Submitted set. An alert naming an unknown metric is refused on save.
The shared alerts suite runs; every telemetry suite is un-gated.

crates/common/src/telemetry/mod.rs

@@ -4,6 +4,7 @@
  * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-SEL
  */
 
+pub mod alerts; // inbuxa: monitoring (MON-25 to MON-30)
 pub mod metrics;
 pub mod tracers;
 pub mod webhooks;